The present invention is related to a ceramic foam insulator with a thermal expansion zone. More particularly, the present invention is related to an effluent gas treatment inlet system with ceramic foam insulator comprising a constant thickness thermal expansion zone.
Treatment of effluent gases is an ongoing problem in the chemical industry. Virtually every chemical process has materials which are undesirable and which must be neutralized, diluted or captured. When highly corrosive materials are utilized, or generated, the problem is magnified.
Particles entrained in an air stream create significant transport problems in a manufacturing environment. It is preferable to insure that all particles remain entrained until reaching the effluent gas treatment zone wherein the particles can be removed in a controlled fashion. Any area of flow disruption or transition tends to cause the particles to settle. A particular area of concern is the inlet of the effluent gas treatment system. It is not uncommon for entrained particles to settle in the inlet. As particles settle they further disrupt flow thereby increasing the rate of particle settling. This is not only undesirable but it is also potentially hazardous when corrosive or environmentally hazardous materials are involved.
A solution to particle settling is provided in U.S. Pat. No. 5,955,037 wherein described is a multi-walled inlet structure comprising an annular outer wall with a porous ceramic inner wall with an annular interior volume there between. Low-pressure gas feed lines in flow communication with the annular interior volume prohibit particle adhesion to the interior walls of the inlet. To the extent that particles still adhere auxiliary high-pressure gas feed lines are suitable for dislodging particles that have adhered. U.S. Pat. No. 5,955,037 is incorporated herein by reference.
The multi-walled structure with interior porous ceramic has proven highly reliable for use in an inlet structure with regards to substantially decreasing particle adhesion. Unfortunately, the structure still has deficiencies which have limited the use in certain instances.
In many manufacturing processes the effluent passing through the inlet has a very high temperature. In practice, the temperature fluctuation causes the porous ceramic to expand and contract. As would be readily realized the expansion and contraction leads to structural cracks and eventual breakage of the porous ceramic interior walls. This is highly undesirable due to the cost and the down time associated with replacing the ceramic.
The use of expansion slots in ceramics is known particularly in heating elements, substrate supports and the like. For the present application expansion slots have not been considered acceptable since the slot provides passage for particles into the annular interior volume between the interior porous ceramic wall and the exterior wall. Furthermore, an expansion slot provides a low resistance flow path for the air thereby disrupting the flow through the ceramic and defeating the benefit provided by the porous ceramic. It is important that air continues to flow through the entire structure of the porous ceramic to insure that trapped particles are dislodged over the entirety. It has heretofore been considered impossible to provide an expansion slot in a porous ceramic without substantially altering the thickness of the ceramic in any way or without creating areas of low, or no, air flow through the porous ceramic. This problem has been solved by the present invention.